Solving Systems with an Inverse Matrix

Algebra Level 2

A system of equations is given by

$\begin{aligned} ax + by &= 5 \\ cx + dy &= -1. \end{aligned}$

If the inverse of $\left[ \begin{array}{cc} a & b \\ c & d \end{array} \right]$ is $\left[ \begin{array}{cc} 3 & 2 \\ -3 & 1 \end{array} \right]$ , then what is $x + y?$